Ask HN: Why do flight apps show different prices for the same route?

I ran a small test on two routes for the travel date 18 November 2025: New York to London and London to Berlin. Five apps: Skyscanner, Kayak, Google Flights, Expedia, and Wego. Parameters: One adult, economy, USD. Incognito on desktop. I ran all searches within about an hour. I recorded the lowest fare shown on the results page and did not go to checkout. The goal was to see whether prices matched across apps for the same route and date.

Findings, JFK to LHR All showed the same Icelandair flight. Prices: Kayak USD 164. Wego 165. Google Flights 165. Skyscanner 167. Expedia 185. Result counts: Kayak about 973. Wego 610. Skyscanner 270. Expedia 80. Google Flights does not provide an easy way to see a total count, and I didn’t feel like counting manually.

Findings, LHR to BER All showed the same SAS flight. Prices: Wego USD 116. Kayak 117. Skyscanner 118. Google Flights 119. Expedia 128. Result counts: Wego 486. Kayak 408. Skyscanner 156. Expedia 93. Again, for Google Flights, I didn’t feel like counting manually.

Price gaps were small, mostly under 10 percent, but a pattern was consistent. Wego and Kayak were typically the lowest. Expedia was higher for the same flights. Result counts varied widely across apps, which may reflect partner coverage.

If you work on metasearch or airline pricing, what factors most often create these gaps? Partner coverage, fare families, currency handling, cache timing, or OTA markups?

Would love to hear your thoughts on this.